Histocompatability genes will be used as genetic markers in a new analytical procedure, the strain distribution pattern method, to search for and locate genes that determine mechanisms of the cell-mediated immune response toward tumor-specific transplantation antigens of methylcholanthrene-induced sarcomas. The genes will be tested. Tumor- specific antigens will be classified according to the gene(s) determining the immune response toward them, and thereby a systematics of tumor antigens will be developed for correlating with their chemistry.